what is gravitational constant
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It could be the gravitational field constant, which is used on Earth at sea level, its value is 9.8Newtons/kilogram
But more likely, you are asking about the Universal Graviational Constant, which relates force, mass quantities, and distance in Newtons law of gravity.
Force=UniversalConstant*M1*M2/d^2
The value of the Universal Constant varies with different measuring systems, in SI, it is G = 6.67384(80) \times 10^{-11} \ \mbox{m}^3 \ \mbox{kg}^{-1} \ \mbox{s}^{-2} = 6.67384(80) \times 10^{-11} \ {\rm N}\, {\rm (m/kg)^2}
http://en.wikipedia.org/wiki/Gravitational_constant
The gravitational constant, denoted as G, is a fundamental physical constant that appears in the law of universal gravitation, proposed by Sir Isaac Newton. It represents the proportionality between the gravitational force exerted by two objects and their masses, as well as the distance between them.
The value of the gravitational constant, G, is approximately 6.67430 × 10^-11 m^3 kg^(-1) s^(-2). This means that if you have two objects with masses, say M1 and M2, separated by a distance, say r, the gravitational force between them is given by the equation:
F = G * (M1 * M2) / r^2
To determine the value of G experimentally, researchers use a variety of methods. One such method involves using a torsion balance, which measures the twisting force caused by the gravitational attraction between two masses. By carefully controlling other factors and collecting precise data, scientists can calculate the gravitational constant. Over the years, experiments have been conducted by different researchers to refine the value of G, leading to the currently accepted value.
It's important to note that while the value of G is known, the origin or cause of gravity itself is still an active area of scientific inquiry.